<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>绝对定位的固定定位模拟</title>
    <style>
        html,body{
            overflow: hidden;
        }
        .page{
            height:2500px;
            /*overflow: auto;*/
            background-color: #cad53d;
        }
        .fixed{
            position: absolute;
        }
    </style>
</head>
<body>
<div class="page">固定定位元素</div>
<div class="fixed"></div>
</body>
</html>